Merge pull request #37173 from brson/stable-next 1.12.1

[stable] Backports for 1.12.1

6 files changed, 12 insertions, 2 deletions

diff --git a/src/librustc_mir/build/expr/as_lvalue.rs b/src/librustc_mir/build/expr/as_lvalue.rs
index ae5ccbfd820..78330f0b975 100644
--- a/src/librustc_mir/build/expr/as_lvalue.rs
+++ b/src/librustc_mir/build/expr/as_lvalue.rs
@@ -96,6 +96,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
             ExprKind::LogicalOp { .. } |
             ExprKind::Box { .. } |
             ExprKind::Cast { .. } |
+            ExprKind::Use { .. } |
             ExprKind::NeverToAny { .. } |
             ExprKind::ReifyFnPointer { .. } |
             ExprKind::UnsafeFnPointer { .. } |
diff --git a/src/librustc_mir/build/expr/as_rvalue.rs b/src/librustc_mir/build/expr/as_rvalue.rs
index dafc53d3c15..3cd79ee1c5a 100644
--- a/src/librustc_mir/build/expr/as_rvalue.rs
+++ b/src/librustc_mir/build/expr/as_rvalue.rs
@@ -115,6 +115,10 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                 let source = unpack!(block = this.as_operand(block, source));
                 block.and(Rvalue::Cast(CastKind::Misc, source, expr.ty))
             }
+            ExprKind::Use { source } => {
+                let source = unpack!(block = this.as_operand(block, source));
+                block.and(Rvalue::Use(source))
+            }
             ExprKind::ReifyFnPointer { source } => {
                 let source = unpack!(block = this.as_operand(block, source));
                 block.and(Rvalue::Cast(CastKind::ReifyFnPointer, source, expr.ty))
diff --git a/src/librustc_mir/build/expr/category.rs b/src/librustc_mir/build/expr/category.rs
index c19ea0f445a..9671f80f48b 100644
--- a/src/librustc_mir/build/expr/category.rs
+++ b/src/librustc_mir/build/expr/category.rs
@@ -68,6 +68,7 @@ impl Category {
             ExprKind::Binary { .. } |
             ExprKind::Box { .. } |
             ExprKind::Cast { .. } |
+            ExprKind::Use { .. } |
             ExprKind::ReifyFnPointer { .. } |
             ExprKind::UnsafeFnPointer { .. } |
             ExprKind::Unsize { .. } |
diff --git a/src/librustc_mir/build/expr/into.rs b/src/librustc_mir/build/expr/into.rs
index e5930f5a62d..58265b5b0d3 100644
--- a/src/librustc_mir/build/expr/into.rs
+++ b/src/librustc_mir/build/expr/into.rs
@@ -249,6 +249,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
             ExprKind::Binary { .. } |
             ExprKind::Box { .. } |
             ExprKind::Cast { .. } |
+            ExprKind::Use { .. } |
             ExprKind::ReifyFnPointer { .. } |
             ExprKind::UnsafeFnPointer { .. } |
             ExprKind::Unsize { .. } |
diff --git a/src/librustc_mir/hair/cx/expr.rs b/src/librustc_mir/hair/cx/expr.rs
index a61fdb79df8..605798ad44c 100644
--- a/src/librustc_mir/hair/cx/expr.rs
+++ b/src/librustc_mir/hair/cx/expr.rs
@@ -602,8 +602,8 @@ fn make_mirror_unadjusted<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
             // Check to see if this cast is a "coercion cast", where the cast is actually done
             // using a coercion (or is a no-op).
             if let Some(&TyCastKind::CoercionCast) = cx.tcx.cast_kinds.borrow().get(&source.id) {
-                // Skip the actual cast itexpr, as it's now a no-op.
-                return source.make_mirror(cx);
+                // Convert the lexpr to a vexpr.
+                ExprKind::Use { source: source.to_ref() }
             } else {
                 ExprKind::Cast { source: source.to_ref() }
             }
diff --git a/src/librustc_mir/hair/mod.rs b/src/librustc_mir/hair/mod.rs
index 2a5b7d0fb29..cc59346487e 100644
--- a/src/librustc_mir/hair/mod.rs
+++ b/src/librustc_mir/hair/mod.rs
@@ -139,6 +139,9 @@ pub enum ExprKind<'tcx> {
     Cast {
         source: ExprRef<'tcx>,
     },
+    Use {
+        source: ExprRef<'tcx>,
+    }, // Use a lexpr to get a vexpr.
     NeverToAny {
         source: ExprRef<'tcx>,
     },